A technology described in Patent Document 1 mentioned below, for example, is already known as the control device described above. In the technology described in Patent Document 1, when starting a vehicle using drive forces of both an internal combustion engine and a rotary electric machine, a first engagement device is engaged first to start the internal combustion engine using the drive force of the rotary electric machine, and thereafter a second engagement device is engaged to start the vehicle.
In the technology according to Patent Document 1, in which the second engagement device is engaged after the first engagement device is engaged to rotate the internal combustion engine and the rotary electric machine, a reduction in working oil due to simultaneous engagement of the two engagement devices can be effectively prevented. However, there is a difference in rotational speed between engagement members of the second engagement device when the second engagement device is engaged. Hence, in the technology according to Patent Document 1, the second engagement device is controlled to a slipping engagement state until the rotational speed difference across the second engagement device becomes zero with the vehicle speed increased. Therefore, the durability of the second engagement device may be reduced because of heat generated by dynamic friction.
In the technology according to Patent Document 1, in which the second engagement device is engaged after the first engagement device is engaged to start the internal combustion engine, the timing when the second engagement device is engaged so that drive forces of drive force sources can be transferred to wheels is delayed by an amount corresponding to the time required to engage the first engagement device and start the internal combustion engine, which delays a response to a request to start the vehicle.
In addition, the technology according to Patent Document 1 relates to control for the two engagement devices at the start with rotation of the internal combustion engine stopped, and Patent Document 1 does not specifically describe or support control for the two engagement devices at the start with the internal combustion engine rotating.